AdSense RPM vs AdX eCPM: How to Compare Earnings Fairly

When publishers move from AdSense to Ad Manager and Ad Exchange, the first thing they want to know is simple: am I earning more? Answering that honestly is harder than it looks. AdSense reports lead with adsense rpm, Ad Exchange reports lead with eCPM, and the two numbers are calculated on different bases. Put them side by side and you can convince yourself of almost anything. This guide explains what each metric measures, why per-impression and per-page numbers move differently, and a simple method for a fair before and after comparison.

RPM, CPM and eCPM in plain terms

All three are "per thousand" measures. They differ in what is being divided and by what.

• CPM (cost per thousand impressions) is a price, usually seen from the advertiser's side: what a buyer pays for a thousand impressions.
• RPM (revenue per thousand) is the publisher's view. Google defines it in AdSense as your estimated earnings divided by the number of page views, impressions or queries, multiplied by 1,000.
• eCPM (effective CPM) is revenue divided by a count of ad events, multiplied by 1,000. Google's explanation of Ad Exchange eCPMs states the base definition as revenue per one thousand impressions.

Google adds an important line to its RPM definition: RPM does not represent how much you have actually earned. It is a ratio built on estimated earnings, which is why the same report can show a different figure a few weeks later.

Page RPM vs impression RPM

The denominator changes the meaning completely. Google's own worked example shows both versions:

• Page RPM = (estimated earnings / page views) x 1,000. In Google's example, an estimated $0.15 from 25 page views gives a page RPM of $6.00.
• Impression (ad) RPM = (estimated earnings / ad impressions) x 1,000. In Google's example, an estimated $180 from 45,000 ad impressions gives an ad RPM of $4.00.

These figures illustrate the arithmetic only; they are not benchmarks. The point is that page RPM tells you what a page view is worth to you, all ad units included, while impression RPM tells you what a single ad impression is worth on average.

In Ad Exchange reporting the choice of denominator is even more visible. Google describes three eCPM metrics, based on ad requests, on responses served (matched requests) and on impressions. Its explanation is worth remembering: fewer impressions are seen than requests are made, because not every request finds a matching ad, not every ad served is rendered, and fewer still are seen. As Google puts it, the further down that chain you choose your denominator, the higher the CPM. The default, Ad Exchange average eCPM, uses impressions, so it is naturally higher than a request-based eCPM on the same revenue.

Why per-impression and per-pageview numbers diverge (ads per page, fill, viewability)

Page RPM and eCPM can move in opposite directions. Three factors are worth checking first.

Ads per page. Page RPM rises when each page view produces more paid impressions; eCPM does not care how many there are. If you remove two low-value ad units, eCPM may go up because the remaining impressions are worth more on average, while page RPM and total revenue go down. The reverse is also true: adding units can lower eCPM and still raise page RPM.

Fill. Google notes that a request-based eCPM factors in fill rate, while impression-based eCPM ignores requests that were never filled. A setup that fills fewer requests at higher prices can show a strong impression eCPM and a weak page RPM. When you compare, look at how many requests turned into impressions, not only at what each impression earned.

Viewability. An ad that is served but never scrolled into view still counts as an impression in many reports. Google's viewability guidance uses the IAB definition: for display ads, 50% of the ad's pixels in view for one continuous second (30% for ads larger than 242,000 pixels). Google also notes that advertisers increasingly ask to buy viewable impressions. Layout changes that improve viewability can change eCPM without any change to traffic. See ad viewability basics for more.

The lesson: no single ratio tells the whole story. Total revenue, page RPM, impressions per page view and eCPM together do.

Estimated vs finalized numbers

Every figure you see during the month is an estimate. In AdSense, earnings are finalized at the start of the following month. In Ad Manager, Google identifies accounts that reached the payment threshold on the last day of the month, and the previous month's revenue is posted to your Transactions page by the 2nd.

Between estimate and final, deductions can apply. Google says Ad Manager earnings may be adjusted for invalid clicks or impressions, implementations that do not follow the Ad Manager Partner Guidelines, or advertisers who fail to pay. Deductions can also arrive later; Google says a deduction may take 30 days or more to appear after its investigation.

For a fair comparison, use finalized monthly totals wherever you can, and treat daily estimates as directional. Comparing a finalized AdSense month with a partial month of estimated Ad Exchange revenue favors whichever side you want to win.

If you joined through an MCM partner, there is one more adjustment: compare your share after the agreed revenue share, not the gross figure in reports. That is the money that reaches you.

A fair before/after method (same pages, same weeks, same geos)

Treat the switch like an experiment. The goal is to change one thing (how ads are sold) and hold everything else as steady as possible.

1. Fix the page set. Choose the pages you will compare, ideally your main templates and your top pages by traffic. Use the same set before and after.
2. Match the calendar. Compare equal-length periods that avoid holidays and big seasonal shifts. Same weekdays, ideally the same weeks of the month. A comparison that straddles a seasonal change, such as December against January, mixes the season into the result. If you can, also compare with the same weeks a year earlier.
3. Match the audience. Split results by country, or at least by your top regions, and by device. A shift in traffic mix toward lower-paying regions can look like a platform problem when it is not.
4. Hold the layout. Do not redesign, add or remove ad units during the comparison. If you must change layout, run a separate comparison for that change.
5. Allow time to settle. If you are still changing settings such as pricing rules in the first days after the switch, leave those days out of the comparison.
6. Use page RPM as the headline. Then use impressions per page view, fill and eCPM to explain the result.
7. Confirm with finalized totals. Revisit your conclusion once the month's figures are final.

What to put in a simple comparison sheet

A spreadsheet with one row per period (or per week) and these columns is enough:

Fill it in for the AdSense period and the Ad Exchange period using the same definitions. If a column is missing for one side, leave it blank rather than mixing in a figure calculated a different way.

Common misreadings

• Comparing AdSense page RPM with Ad Exchange eCPM. Different denominators. Compare page RPM with page RPM.
• Comparing estimates with finalized numbers. Wait for final figures, or compare estimates with estimates.
• Reading a higher eCPM as a win. It may come from fewer impressions. Check total revenue and impressions per page view.
• Ignoring traffic mix. A change in the countries or devices your visitors use can move RPM on its own, with no platform change at all.
• Forgetting the revenue share. Under MCM, compare your share, not gross revenue.
• Using too short a window. A few days can be swamped by normal swings. Use full weeks, ideally a full month.

If your RPM was already dropping before any switch, read AdSense low RPM causes first; the cause may have nothing to do with the platform. For realistic expectations about the move itself, see will AdX earn more than AdSense.

Next step

A fair comparison method lets you judge Ad Exchange on real numbers instead of hopes. If your site is ready to make the move, eligible publishers may receive an MCM invitation, subject to Google's policies. Check the requirements, then Get AdX access to request a review.